Having introduced the subject of comparing religions, we will now analyze the first question:
1. Has the religion persuaded a significant fraction of the world population, outside a single ethnic group, to believe in it?
One of the reasons for this question is that few people have time to investigate all of the numerous religions that exist. (I've done more than most people ever will, but there are still huge gaps in my knowledge.) Since it is not possible to do a complete analysis of every religious tradition, one must have some way of sifting out the more likely candidates from the less likely ones. Whatever criterion one uses for this sifting, it has to be something which can be measured prior to doing an in-depth investigation.
In persuasive writing, it is generally considered most rhetorically effective to lead with one of your stronger arguments, so that people don't dismiss your case out of hand. But here, the nature of the subject requires me to lead with one of the weaker arguments for a religion, namely its popularity. But it is not so weak that it doesn't deserve careful consideration. Later on, we will discuss some more dispositive tests.
Ad populum (appeal to mass belief) is not necessarily a fallacy, when it is used only as a probability argument rather than a deductive argument. I would never say that a large number of adherents guarantees that a religion is correct; obviously not. Many completely wrong beliefs (e.g. homeopathy and astrology) still have lots of people who swear by them. There are, however, some cogent reasons why a true religion is likely to have more adherents than it would if it were false. So while the fact that a significant fraction of the world population believes in something cannot (taken by itself) be enough reason to accept it, I do think it justifies taking it seriously enough to investigate its truth.
All Else being Equal, Truth is More Convincing
Presumably a true religion is more likely than a false one to be found convincing by a broad range of people. It is also more likely to be regarded as important enough to share with others. While human beings are far from infallible, it says something good about a religion if it can pick up a large number of voluntary converts. At least some people take into account reason and evidence (and any "signs" they may happen to witness) when deciding what to believe; so all else being equal, truth should provide a religion with a survival advantage. (If this were not true, then there would be very little point in writing blog posts analysing the evidence for or against religion, because nobody would take them into account.)
It is especially impressive if a religion has been found plausible by people from many different cultures and backgrounds. A religion might take off in a single ethnic group because of some fluke of history. On the other hand, a multicultural distribution suggests that perhaps the religion contains something true to life, that it is in some way suited to the human condition at large, not just one cultural milieu. If it has seemed insightful to many kinds of poets, philosophers, and peasants, then it probably contains at least some element of universally valid truth.
A Census of World Religions
If even 1 in a thousand people (worldwide) investigate religions in a sufficiently sensible and open-minded way to identify the truth (whatever it is), then it would follow that the true religion must have at least 7 million adherents or so, which would narrow us down to about a dozen possibilities (according to the website adherents.com in 2014.) If you scroll down past the pie chart of the first link, you'll come to the following list:
- Christianity (2.1 billion)
- Islam (1.5 billion)
- Secular/Nonreligious/Agnostic/Atheist (1.1 billion)
- Hinduism (900 million)
- Chinese traditional religion (394 million)
- Buddhism (376 million)
- primal-indigenous (300 million)
- African Traditional and Diasporic (100 million)
- Sikhism (23 million)
- Juche (19 million)
- Spiritism (15 million)
- Judaism (14 million)
- Baha'i (7 million)
[+additional religions with 4.2 million religions or fewer]
Of course, many of these categorization decisions are questionable. Nonreligious is by definition the absence of a religious commitment (although Communism might be regarded as a religious substitute for a substantial minority of these people); Chinese traditional represents various admixtures of Buddhism, Taoism, Confucianism, and ancestor worship; indiginous or African traditional are umbrella terms for thousands of different pagan religious traditions (most of which would have less adherents than Baha'i if taken individually); while Juche is just the state ideology of the North Korean dictatorship (which has approximately the same moral credibility as Nazism). Fringe Christian or Islamic cults might be better regarded as separate religions, and some of them (like Mormonism) I will be treating as separate religions in subsequent posts. But the exact division is not very important. The point is that there are really only a small number of options on the table, if you use the rest of humanity to sift out the options that have been found most plausible.
(That being said, if there is some particular religion with fewer adherents that you have some reason to think is specially promising, I'm not saying that you shouldn't investigate it. But it is reasonable to start with more popular religions.)
Another Reason to Consider Popularity: Divine Favor
A true religion is also more likely to have divine favor assisting its spread across the world (assuming of course that the religion is theistic). I don't want to put too much emphasis on this, since the worship of strength and worldly success is one of the crudest of all religions. My own religion centers around the Cross, therefore it is (or ought to be) on the side of the unjustly persecuted everywhere. Might does not make right. Yet sometimes, when human hearts are receptive, right makes for might. Truth may be weak, but sometimes this weakness is itself a paradoxical form of strength, as Gandhi showed in India, and the Civil Rights Movement showed in America.
If there is a religion revealed by God, then it is an obvious sociological fact that not everyone on earth has accepted the message. For whatever reason, it is not the divine will to overawe everyone into accepting it (at least, not yet). But if it is a genuine revelation, one expects that he would protect and defend it to some extent, at least enough to accomplish whatever goals he has in revealing the message.
At the very least, extinct religions like e.g. Greek or Egyptian polytheism are probably not worth taking very seriously—if those gods are at all real, why would they have allowed their names to be completely forgotten, except as fodder for dissertations, garden statuary, and comic books? It took a lot of kahunas for the prophet Jeremiah, way back in the 600s BC when the Jews were surrounded by polytheists, to taunt the followers of other gods by telling them (in Aramaic, the international language):
“These gods, who did not make the heavens and the earth, will perish from the earth and from under the heavens” (Jer 10:11).
But in quite a large portion of the globe, including of course the Middle East where Jeremiah was prophesying, this is exactly what has happened. (This process is not yet complete, but if a prophet had predicted that all the world would one day consist of blue-skinned people, and then over the next few centuries half of the people on the planet had turned blue, I would start taking the rest of what he said more seriously, even if it hadn't yet happened to everyone!)
The Jewish Origins of the Idea of Progress
Historically, it was extremely unusual, in the pre-Christian world, for a religion to predict its own global dominance. As moderns we think that every ideology should predict a future in which it is more widely successful, but that's not how most people thought back then. The ancients usually expected that the world would keep on going more or less as it was before, or maybe keep getting gradually worse. As Westerners we are used to ideologies having an eschatological aspect—looking forward to a future utopian society that is a radical improvement on the present—but the reason we think this way is precisely because of the influence of Judaism! (The only other eschatological pre-Christian religion I know of is Zoroastrianism, which presumably either got it from Judaism, or else influenced Judaism in this respect.)
Universal vs. Ethnic Religions
The Jews did not (and still do not) regard it as necessary for pagans to become Israelites in order to be saved. The Hebrew prophets spoke against idolatry and polytheism, but they foresaw the worldwide acceptance of pure Monotheism as a sign of the future Messianic Era, not as a realistic goal for the present day.
However, at the time of the Roman Empire, there were a large group of "God-fearers", who came to believe in the truth of Judaism, but did not formally convert due to the burdensome nature of Jewish ritual. A lot of these people later became Christians, once it became clear that you didn't have to become a Jew in order to be a full member of the Christian Church.
If this model is right, then God cultivated an ethnic religion for a limited period of time, in order to produce the right circumstances in which the Messiah could come. But now that he has come, Christianity is a religion for all people, in fulfilment of God's promises:
“It is too small a thing for you to be my servant
to restore the tribes of Jacob
and bring back those of Israel I have kept.
I will also make you a light for the nations,
that my salvation may reach to the ends of the earth.”
Hence, if we wish to find a worthy rival to Christianity, it should probably be a universal religion, i.e. its message should be sufficiently relevant to the perennial human condition, that it can be adopted by people from every culture and tribe, without completely wrenching them out of their social context. A religion cannot really be considered cosmic in scope, if it isn't even able to be cosmopolitan. This criterion rules out a large number of purely ethnic and tribal religions.
If God were still restricting his message primarily to a single ethnic group, presumably the rest of us would not be judged too harshly for not being in on the program. Even the insiders might not think you have a moral obligation to join their group. This makes it a lower priority to investigate ethnic religions such as Judaism or Hinduism (unless of course you happen to belong to one of these groups already).
As the most extreme case of ethnic exclusion, some religions currently forbid conversion altogether, for example traditional Parsees (Zoroastrians in India), and the Druze (in the Middle East). These religions also forbid their adherents to marry outsiders. There's just no way to get in, even if you wanted to!
Other religious traditions teach that God reveals himself through all cultures and therefore it is counterproductive to cast aside your ancestral teachings in favor of theirs. These religions may discourage converts: for example, a woman from the church I grew up in became interested in Hinduism, and went to India to study under a guru. He told her to go back to the USA, saying that she wasn't done being a Christian yet! I've heard other anecdotes along similar lines, so apparently this attitude is fairly common among Hindu teachers.
Then there are various small religions (such as Baha'i, which is right on the edge of my somewhat arbitrary 1/1000 threshold) that are clearly intended to be international in scope, but have failed to achieve a very large number of converts to their cause.
(In some cases this might be because the religion is new. Of course all religious movements start out small, so we can't place too much weight on this criterion or it would imply that nobody should have followed Jesus at the beginning, when he only had a few disciples. At the same time, it seems reasonable to say that an untested charismatic cult leader needs to clear a higher bar than a well-established religious tradition.)
Hence, to score top points on this criterion, it is best to have already convinced a significant fraction of the world.
The Three Big Evangelical Religions
These considerations suggest we should focus the most attention on Christianity, Islam, and Buddhism. These are the 3 world religions which have had the most success in gaining converts even in radically different cultures, the ones whose message has been perceived as "Good News" to numerous people groups around the world. (But I will still try to say some things about other religions as well, to the extent that my limited knowledge allows.) To what extent their religious teachings actually are good news—well, that is a subject for the later posts!
Of these three "evangelical" religions, the spread of Islam is somewhat marred by the fact that the early spread of Islam, starting during Mohammad's lifetime and continuing for several centuries thereafter, was largely due to military action and subsequent cultural imperialism. Although obviously Muslims would attribute this rapid spread to God's will, from a human point of view it seems that the sword discriminates among truths far more clumsily than rational discourse does. (There are however a few countries, such as Indonesia, where the spread of Islam seems to have largely occurred through peaceful means such as trade.)
Of course some Muslim historians will insist that each of these conquests was morally justified by various particular circumstances. But, to paraphrase a bit of popular wisdom: anyone might meet one or two jerks, but if everyone you meet seems to be a jerk, then you should consider the possibility that you might be the jerk, and they're just reacting to your personality. In particular, any group that tries to conquer large parts of the world by the sword, should not be too surprised when the other countries look on with dismay and try to fight back. (Here I am speaking historically, and not attempting to justify any particular modern wars.)
It actually took several centuries for these conquests to result in a majority for Islam in the Middle East and North Africa. At first it was mainly the rulers of the conquered lands who were Muslims. While pagans were required to convert at swordpoint, monotheistic groups such as Jews, Christians, Mandaeans (yes, there still exist followers of John the Baptist who never converted to Christianity!—although by now they have become very gnostic and reject even Moses), and Zoroastrians were generally tolerated, so long as they accepted second-class citizenship (dhimma), paid extra taxes (jizya), and did not try to convert Muslims to their religion. Over the long run these legal disadvantages gave Islam a decisive advantage.
Mind you, at times the situation for Jews or "heretics" in medieval Europe was even worse than this. It is easy to find examples of persecution of religious minorities in Christian history. (Officially speaking, the Roman Catholic Church hierarchy only asserted authority over baptized individuals, but sometimes local rulers would impose Christianity on their domains, and then later the Church would try to enforce orthodoxy in these populations since they were now "Christians".)
Even Buddhists have sometimes engaged in religious persecution, e.g. historically in Japan, and at the present in Myanmar (a.k.a. Burma). A college friend once tried to argue to me that anyone who persecuted other people wasn't a real Buddhist and therefore didn't count. But this was an obvious use of the No True Scotsman ploy. In my opinion the Christians who persecuted people weren't in that respect very good examples of Christianity either, but they still existed.
However, I think it is fair to say that both Christianity and Buddhism usually spread to new cultures primarily through evangelism. This is especially true in their early years, and also in the contemporary world.
For example, after converting to Buddhism, the Indian king Ashoka (formerly a cruel tyrant) seems to have become a pacifist who promoted religious toleration (although there are some contrary traditions whose accuracy is disputed); his support for missionary activity in other countries helped spread Buddhism to many other nations. And for the first 3 centuries the Christian Church rapidly expanded, even though it had no control over the government and intermittently went through periods of severe persecution, prior to its legalization by the first Christian Emperor, Constantine.
Of course there were plenty of instances of persecuting others which occurred after these religions were well-established. But it is open to both Buddhists and Christians to claim that the persecutors were bad examples, that they were ignoring the explicit instructions of their own sacred texts, and ought to have known better. And perhaps that, in the long run, their religion would have advanced just as well or even better, without the aid of violent support. It is not really open for a Muslim to say the same thing, because then they would have to disown their own Prophet and his immediate followers. Of course they can still renounce particular instances of expansion through warfare, as being done in an inappropriate time or manner, but they cannot renounce it on principle.
(Christians do have to deal with divinely commanded warfare in the Old Testament, although this was not for evangelical purposes and was geographically limited. There was no command to spread Judaism to other nations by conquest! I will reserve discussion of the ethics of this violence until later, but it does introduce our next topic, namely continuity with other religions.)
Next: Ancient Roots